<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <button id="btn1">按钮</button>
  <script>
    function show(a, b) {
      console.log(this);
      console.log(a, b);
    }
    // show(20, 40)

    // show.call("call", 10, 34)
    // show.apply("apply", [20, 44])
    var res = show.bind("bind")
    // res(20, 44)

    var btn = document.getElementById("btn1")
    // btn.onclick = function() {
    //   show.call("call")
    // }

    // btn.onclick = function() {
    //   show.apply("apply")
    // }
    btn.onclick = res
  </script>
</body>

</html>